Radial piston machine

ABSTRACT

A radial piston machine having a casing formed with radially disposed cylinders containing pistons and a cam shaft which is rotatably mounted in the casing and guide shoes carried by the piston and engaging on the cam so that the transmission of power between the cam shaft and the piston takes place through the guide shoe.

United States Patent Biernath et al. June 20, 1972 [541 RADIAL PISTON MACHINE [56] References Cited [72] Inventors: Emil Blernath, Stuttgart-Oberturkheim; UNITED STATES PATENTS Hans Burkard, Stuttgart, both of Germany 2,426,100 8/l947 Holden et a]. ..91/491 [73] Assignee: Excentra Gesellschaft mit beschrankter 3 135 222 3113;; giggg s "Z2223 gg zg Amflebe Fenbach l:321:086 11/1919 camel-van ..9l/496 2,877,662 3/l959 Woydt.... ..74/569 [22] Filed: May 28, 1970 3,407,707 10/1968 Belliel'e ..92/72 [2]] App! Primary ExaminerMartin P. Schwadron Assistant Examiner-Ronald H. Lazarus [30] Foreign Application Priority Data y*- & Stem May 31, 1969 Germany ..P 19 27 807.0 57 S T [52] us Cl t 92/72 74/569 91/496 A radial piston machine having a casing formed with radially 5 n Int Cl I d 1/00 disposed cylinders containing pistons and a cam shaft which is 58] Fig. 491 rotatably mounted in the casing and guide shoes carried by the 123 l 4 1 piston and engaging on the cam so that the transmission of power between the cam shaft and the piston takes place through the guide shoe.

10 Claims, 7 Drawing Figures SHEET 2 [IF 6 WMM SHEET 3 OF 6 PATENT'EDJUH 20 m2 MMMWMZ P'ATFiNTEl'lJuuzo 1972 SHEET 5 OF 6 PATENTEDJuxau I972 SHEET 6 OF 6 RADIAL PISTON MACHINE The invention relates to a radial piston machine, in particular a radial piston pump, including a casing with radial cylinders containing respective pistons, the pistons engaging an internal cam. However, it is also possible for the radial piston machine to operate as a motor or to arrange the cylinders inside a surrounding cam.

In accordance with the invention a radial piston machine comprises a casing, generally radially disposed cylinders within the casing, a cam shaft carrying a cam rotatably mounted in the casing, pistons occupying the cylinders respectively and guide shoes connected to piston rods for the pistons respectively, the guide shoes engaging on the cam so that a transmission of power between the rotating cam shaft and the pistons takes place through the guide shoes.

Each guide shoe is preferably pivotable with respect to a guide shoe shaft, whose ends are guided in two slots of a stationary component of the machine, running in the direction of the axis of the cam, and that the components providing the slots are directly seated on the casing members supporting the cam shaft bearing.

With the arrangement of this invention the necessity for ac curately aligning several constructional components is avoided.

The arrangement according to the invention makes it possible to utilize to the full the bearing capacity of the segment bearing box of the guide shoe. Also by means of the measures according to the invention, independent of any errors of manufacture or assembly, it can be ensured that the segment bearing box of the guide shoe can on each occasion adapt itself better to the sliding surfaces of the cam. The greater bearing capacity thus achieved allows an increase in efficiency of the machine with constant dimensions of the casing.

Due to the guidance of the guide shoe shaft by means of cross-heads in the said slots, the plane of movement of the guide shoe shaft can, with little technical work and greater accuracy, be adjusted and maintained parallel to the cam shaft axis. However, a displacement or oblique position of the guide shoe axis with respect to the cylinder axis is not excluded. In order to prevent detrimental effects to the piston and cylinder due to such a displacement or oblique position, the present invention is further developed such that the piston rod supporting the guide shoes is axially displaceable in a longitudinal bore of the piston, it abuts against the base of the piston with its head and around its head is pivotable but limited radially.

Thus the invention conveniently provides that when it is stationary the guide shoes are held in contact with the cam by one or more rings surrounding the guide shoes and rotatable with the cam, and that these rings are disposed in a region, in which the inertia produced by the reciprocating motion of the piston is directed towards the cam, the rings being interrupted for the purpose of unrestricted insertion and removal of the guide shoes.

Generally, relatively great forces must be applied by the springs serving for the return of the piston, since they have to overcome the forces of inertia produced by the reciprocating motion of the piston and guide shoe, in order to keep the guide shoe constantly in contact with the cam. Therefore, the use of springs has the disadvantage that particularly with high rotational speeds and with large pumps, in which these forces of inertia are very high, more space is required for the springs. A great advantage of the construction according to the invention is that the removal and insertion of the piston and guide shoe is greatly facilitated in that a radial extraction of a piston is possible, without the return rings being axially displaced previously, which avoids a complete dismantling of the entire pump.

According to the invention, the one or two rings used for the return of the guide shoe during the intake stroke are interrupted at a point, and the dismantling aperture thus created is located inside a region of the ring, in which the forces of inertia produced by the reciprocating motion of the piston guide shoe are directed towards the cam, so that during the running of the machine at the dismantling aperture there is no danger of the lifting of the guide shoe from the cam. This is also the case in the region of the lower dead center position of the guide shoe. The interruption of the ring, for reasons of stability, only occurs appropriately in the part of the ring, which surrounds the guide shoe, in order that the whole ring as such is not interrupted. Solely during a stoppage of the machine could a guide shoe located in the lower region of the machine fall out of this constructional gap as a result of its own weight. However, according to a further embodiment of the invention, this is opposed by the arrangement of a spring, which, since it only needs to hold the specific weight of the guide shoe, can be very weak and therefore small, and which therefore as a matter of expense is of no consequence; or even by an embodiment, in which only one ring is interrupted and the removal of the second uninterrupted ring can be achieved by a slight axial displacement of the guide shoe. The same applies for a radial piston motor.

Finally, the invention preferably also comprises a radial piston pump, which is characterized in that it has channels guiding pressure oil from the cylinders to an outlet aperture, in a rotating or stationary steel body and that the steel body consists of cast steel, in which steel tubes forming the channels are incorporated.

The invention is particularly applicable to such pumps, in which the channels are curved or angular. The invention can be used both in pumps whose channels are arranged in stationary, as well as pumps, whose channels are arranged in rotating steel bodies.

In particular, pumps for very high. outputs and high pressures, whose pump bodies consist of forged steel bodies, with respect to the radial piston pumps according to the invention, necessitate a high manufacturing cost. The invention avoids forming the channels with the help of sand cores during casting. This embodiment would impose high casting requirements, since it involves the danger of core displacements, sand pockets or other casting errors on the inner sides of the channels. Such casting errors, such as adhering burnt sand, even with considerable cleaning cannot be reliably removed, so that with high alternating pressures which are normal during operation, the danger of chipping off of such parts exists, due to which the reliability of operation of the pump is jeopardized.

With the construction according to the invention the pipes become welded to the cast steel body, so that they both increase their rigidity. It is appropriate to co-ordinate the carbon steel of the pipes and the cast material such that the melting point of the steel pipe material is slightly higher than the melting point of the cast steel material poured in. Due to this, the fusion of both parts is promoted. If, before casting, the pipes are filled with a material, which does not melt during casting, and by packing or the like this material is made quite compact, then this material opposes the danger of the compression of the pipes during casting. Thus if there is used as such a material, a reducing material, then a scaling of the inner side of the pipe or channel is avoided.

The drawings show embodiments of the invention,

FIG. I is a partial section through a radial piston machine,

FIG. 2 is a section on the line II II of FIG. 1,

FIG. 3 is a plan view of the cam with the cam shaft and two guide shoes engaging the cam.

FIG. 4 is a slightly modified embodiment of FIG. 3,

FIG. 5 is a section on the line VV of FIG. 4 during the insertion of the lower guide shoe,

FIG. 6 shows the arrangement of the parts shown in FIGS. 4 and 5 inside a pump casing, and

FIG. 7 is a vertical axial section of the cast steel casing of a radial piston pump.

A shaft 1 with a cam 2 is mounted according to FIGS. 1 and 2 in a cam shaft bearing 3 constructed as a cone or roller bearing, which is supported by an annular casing member 4. The casing member 4 is attached, by means of screws, which are indicated in the drawing by lines 5, to a casing 6 and supports a component 8 having a diametrial pair of slots 7. Thus the latter sits directly on the casing member 4 supporting the cam shaft bearing 3 and therefore can be relatively easily brought into alignment with the axis 1a of the cam shaft 1, and in particular, such that the imaginary connecting lines of the walls 711 of the two slots lying opposite each other, respectively forming a guide shoe, run exactly parallel to the axis 1a of the cam shaft 1. The attachment of the annular component 8 to the annular casing member 4 is efiected by means of screws, which are indicated in the drawing by lines 9.

Against the walls 7a of the slot there runs a roller acting as a cross head 10 which is rotatable on a bearing part 11 of the guide shoe axis 12 and whose diameter corresponds with slight play to the distance between the two walls 7a, or even a corresponding slide ring. The guide shoe shaft 12 supports a tiltable guide shoe 13 and is itself secured in a fork 14 of a piston rod 15, whose head with a hemispherical contact surface 16 abuts against the base 17 of an inverted piston 18, which runs in the lapped bore 19 of a casing cover 20. The latter member sits on the casing 6. There are supported against its springs 21 and 22, which urge the guide shoe 13 against the cam 2 as well as urging the inverted piston 18 against the piston rod 15. 24 refers to the axis of the cylinder bore 19 and 24a refers (in an exaggerated manner) to a somewhat oblique position of this bore in relation to the axis 1a of the shaft. 12a refers (in an exaggerated manner) to an oblique position of the guide shoe axis, which will occur, if the axis 240 of the bore is not exactly vertical to the axis In of the shaft.

By way of contrast to the embodiment illustrated, the component 8 providing the slots 7 can be constructed as a split ring, or there can be provided several components with slots 7, each such component being attached by means of screws to the annular casing member 4 and respectively providing slots for the cross head 10. Furthermore, the annular casing member 4 does not necessarily need to be in one piece, but can be composed of several pieces, or can be integral with the casing 6. However the annular shape of the casing member 4 and of the component 8 gives the greatest constructional advantages.

Due to the provision of the slots 7 in relation to the axis of the shaft, disposition of the guide shoe obliquely in relation to the axis of the cam does not impose forces on the parts. Due to the use of the arrangement illustrated and described a better utilization of the bearing capacity of the guide shoe is achieved, since the specific load can be made to be equal and maximal at all points.

A further pressure can occur with a rigid connection between the piston and the piston rod, and in particular with lateral displacement of the cylinder axis 24 in relation to the guide shoe axis 12. This pressure is removed by means of the inverted piston arrangement. A third pressure can also occur due to an oblique position of the cylinder axis (24 to the position 240) in relation to the axis la of the cam shaft. This pressure is also removed by the inverted piston 18.

Previously the slot was provided directly in the cylinder. At great expense the cylinder had to be constructed to be in alignment with three axes. Namely, the cylinder had to be exactly central and exactly vertical in relation to its guide slot and the slot had to be exactly parallel to the axis of the shaft. As regards the central position in relation to the axis of the shaft and the vertical position in relation to the axis of the shaft a simplification is provided by the inverted piston. Now, if the slots are arranged as illustrated and described, then the problem of the parallel alignment of these slots to the axis of the shaft is considerably reduced. Increased economy is thus ensured by the provision of the slot 7 illustrated and described, since the latter makes it possible to allow greater tolerances in the two other conditions where accuracy of the cylinder is required.

In the embodiment according to FIG. 3 a cam 31 is seated on a driven shaft 32. Guide shoes 33a, 33b abutting against the cam 31, are, as the upper guide shoe 32a shows, held by two rings 34a,34b, which are secured to the cam 31 by screws according to the line 35. The rings 34a, 34b have an annular flange, which engages over the ends 37 of the guide shoe, so that the guide shoes 33a, 33b are always held against the cam. Piston rods 38, which act on the pump pistons, not shown, engage the guide shoes. Now the ring 34b in the lower right-hand part is interrupted in the flange part and in such a way that it is possible to displace the guide shoe 33b laterally in the direction of the axis of the cam shaft (c.f. arrow 39), from a position corresponding to that of the guide shoe 33a so far that the end 40 of the guide shoe is released from a flange 41 of the ring 34 a. The guide shoe can then be removed in a direction at right angles to the axis of the cam shaft.

FIGS. 4 and 5 show an embodiment which is somewhat different to that of FIG. 3, in which flange parts 42a of two lateral rings 42 are interrupted in the region in which the inertia arising from the reciprocating motion of a guide shoe 43 and piston is directed towards the cam 36. Thus the guide shoe 43 can be inserted in the direction of the arrow 44 (FIG. 5) in the recess of the flange parts 42a of the ring 42 and for the greatest part of one revolution of the cam is held by the ring 42. In the annular position shown in FIG. 5 a holding of this type is not necessary, since at this point the guide shoe and piston, as a result of the moment of inertia of these parts, abuts against the cam during the rotation. Furthermore, when the machine is stationary a spring (not shown) serves to hold the guide shoe.

FIG. 6 illustrates the arrangement of an embodiment according to FIG. 4 inside a radial piston pump casing. A shaft 1 with the shaft axis 1a supports a cam 2. The shaft 1 is mounted in bearings 3. The parts of the pump located on the left of the axis 24 are substantially like those located on the right hand side of the axis 24 and shown here. The shaft bearing 3 is seated through the intermediary of an annular casing member 4 in the casing 6, to which it is connected by screws on the line 5. In this casing there is seated a split ring 8 connected to the annular casing member 4 by screws on the line 9, which has radial slots 7, in which a cross head 10 of a bearing 11 for the guide shoe shaft 12 can move up and down. The guide surfaces of the slot 7 in the annular component 8 are referred to by 7a. A guide shoe 13 can pivot on the guide shoe 12. The shaft 12 is thus seated in a fork 14 of the piston 15, which is in turn seated in a piston hood or an inverted piston 18, in relation to which it has some play. The piston cover 18 is slidably mounted in a cylinder bore 19. This bore is located in a casing cover 20, which rests on the housing 6. The cylinder bore 19 opens into a pressure chamber 50, which is provided with a suction port 51 and on the left-hand side (not shown) with an outlet aperture for the pressure. The inverted piston 18 has a base 52, which is pushed downwards by a comparatively weak spring 53, which acts against the casing cover 20. In addition, another weak spring 54 is provided, which also acts against the casing cover and presses, by means of a ring 55 on the fork 14, so that the guide shoe 13 always abuts against the cam 2. This spring only needs to hold the true weight of the guide shoe and piston when the machine is stationary, if a guide shoe located in the lower region is disposed exactly in alignment with an interruption in the holding ring 56 when the machine is stationary. The holding ring 56 corresponds to that in FIG. 4. The recess 42a shown there can, with slow rotation of the cam, be turned one after the other past all the guide shoes, so that one guide shoe after the other can be removed. However, it is particularly advantageous that in this way it is also possible to remove an individual guide shoe together with the guide shoe shaft 12, piston 15 and fork 14, in which case the dimensions of the parts 13,12,15 and 14 must naturally be kept such that they can be removed through the aperture 25. This occurs after removing the casing cover 20 from the casing 6.

In an embodiment of a radial piston engine according to FIG. 3 there is required in the axial direction of the cam shaft a little more freedom of movement, in order that the pump piston together with the guide shoe and guide shoe shaft can be lifted out in an upwards direction after the removal of the casing cover 20.

According to FIG. 7 in a bore 61 there are arranged bearings for the cam shaft. In bores 62 there are seated pump cylinders, whose pistons are supported against the cam of the cam shaft. There is provided in the casing wall an annular channel 63, which by means of several lateral channels 64 through bores 65, in which there are located non-return valves, is connected to the bores 62, which are in turn closed off at their ends by suction valves. 66 refers to an outlet channel, which leads outwards from the annular channel 63 and is connected to the compressed air pipe. The side channels 64 and the channel 63 are welded together from steel tubing be fore the casting and are arranged in the cast cavity. Now if the casing is filled with molten cast steel, then a rigid welded connection is formed between the tubes forming the channels 63 and the side channels 64, which consist of carbon steel and the cast steel, which forms the casing. Before the insertion and securing of the pipe system 63,64 in the cast shape the pipe system has been tightly filled, and preferably with a reducing substance, which avoids an oxidation of the inner wall of the pipe system and therefore can contribute to preventing the complete melting or too extensive softening of the tube wall during the recasting with cast steel, since immediately after the casting it draws some of the heat from the pipes and finally where there is danger of compression under the weight of the mass of cast steel it provides for the pipes a support acting from the inside outwards. After coding, the steel bodies and the pipes form a rigid, mutually supported entity, whose fusion cannot be destroyed even by heavy ,altemating loads and changes of temperature.

The embodiment and manufacture of a pump just described and illustrated finds particular application in machines with more than two cylinders. Then the number of cylinders naturally corresponds to the number of side channels.

We claim:

1. A radial piston pump with radial cylinders surrounding an inner rotatable cam, guide shoes engaging the cam, piston rods connected indirectly with the guide shoes respectively, springs pressing the guide shoes against the cam, the guide shoes being pivotable in relation to respective guide shoe axles, the ends of which are guided in pairs of slots in a stationary component, said component having the slots being connected directly with a further part of the housing by means of screw connections said further part supporting bearings for the cam shaft.

2. A radial piston pump as claimed in claim 1, wherein the components having the slots are constructed as rings.

3. A radial piston pump as claimed in claim 2, wherein the rings are constructed to be sound isolating and are attached to said housing part in such a way as to dampen oscillation.

4. A radial piston pump as claimed in claim 1, wherein the piston rods supporting the respective guide shoe axles are axially displaceable in longitudinal bores of inverted pistonspower between a shaft on which the cam is provided, and the pistons, by means of the guide shoes, the guide shoes being held in contact with the cam during unloadedstrokes by at least one ring which enclose the guide shoes and rotate with the cam, this ring being interrupted "to permit mounting and removal of the guide shoes and the interruption being in an area in which the inertia caused by the backward and forward motion of the pistons is applied to the cam.

6. A radial piston machine as claimed in claim 5 wherein each of the guide shoes is held against the cam by a pressure spring which holds at least the weight of the piston and guide shoe.

7. A radial piston machine as claimed in claim 5, wherein there are two holding rings one having an interruption which permits the guide shoes to be axially displaced in relation to the cam.

8. A radial piston pump as claimed in claim 1 comprising a housing having cylinders surrounding a cam, in which guide shoes engaging the cam are connected to respective piston rods a rotatable shaft on which the cam is provided, having channels which supply fluid from the cylinders to an outlet in a body, the body being cast and having tubes forming the channels.

9. A radial piston pump as claimed in claim 8, wherein the melting temperature of the material of the tubes is approximately the same as the temperature of the cast material of the body.

10. A process for the production of a cast steel body of a radial pump as claimed in claim 8, pump having tubes cast in it, comprising filling the tubes during the casting with a material which does not melt during the casting and which has a reducing effect. 

1. A radial piston pump with radial cylinders surrounding an inner rotatable cam, guide shoes engaging the cam, piston rods connected indirectly with the guide shoes respectively, springs pressing the guide shoes against the cam, the guide shoes being pivotable in relation to respective guide shoe axles, the ends of which are guided in pairs of slots in a stationary component, said component having the slots being connected directly with a further part of the housing by means of screw connections said further part supporting bearings for the cam shaft.
 2. A radial piston pump as claimed in claim 1, wherein the components having the slots are constructed as rings.
 3. A radial piston pump as claimed in claim 2, wherein the rings are constructed to be sound isolating and are attached to said housing part in such a way as to dampen oscillation.
 4. A radial piston pump as claimed in claim 1, wherein the piston rods supporting the respective guide shoe axles are axially displaceable in longitudinal bores of inverted pistons which are closed at the top by bases, the inverted pistons being axially displaceable in respective cylinder bores and being radially pivotal about their bases.
 5. A radial piston machine comprising a housing and with radial cylinders surrounding a cam, piston rods connected to respective guide shoes which engage the cam to transmit power between a shaft on which the cam is provided, and the pistons, by means of the guide shoes, the guide shoes being held in contact with the cam during unloadedstrokes by at least one ring which enclose the guide shoes and rotate with the cam, this ring being interrupted to permit mounting and removal of the guide shoes and the interruption being in an area in which the inertia caused by the backward and forward motion of the pistons is applied to the cam.
 6. A radial piston machine as claimed in claim 5 wherein each of the guide shoes is held against the cam by a pressure spring which holds at least the weight of the piston and guide shoe.
 7. A radial piston machine as claimed in claim 5, wherein there are two holding rings one having an interruption which permits the guide shoes to be axially displaced in relation to the cam.
 8. A radial piston pump as claimed in claim 1 comprising a housing having cylinders surrounding a cam, in which guide shoes engaging the cam are connected to respective piston rods a rotatable shaft on which the cam is provided, having channels which supply fluid from the cylinders to an outlet in a body, the body being cast and having tubes forming the channels.
 9. A radial piston pump as claimed in claim 8, wherein the melting temperature of the material of the tubes is approximately the same as the temperature of the cast material of the body.
 10. A process for the production of a cast steel body of a radial pump as claimed in claim 8, pump having tubes cast in it, comprising filling the tubes during the casting with a material which does not melt during the casting and which has a reducing effect. 